Mike its funny that you say that. In Florida, A. glabra is native and it is melaleuca trees that are invasive and have taken over vast areas of Florida swamp land. That said Pond Apples spread with ease. Every year I pull out bout 100 hundred trees that sprout naturally around my property.
Adam, my trees are just seedlings from random fruit collected in the Everglades and I've never tried grafting on to them. I am just offering because it seems like a shame to toss all those seeds away.
I will say this about the Pond Apple trees I have, the ripe fruit has an intoxicating smell. Oddly, the smell doesn't transfer into flavor of the fruit and while the taste isnt unpleasant, it has zero sweetness. They are sorta like a snotty cherimoya, with 1/100 the flavor and sweetness.